Device and method for creating a channel in soft tissue

ABSTRACT

Medical devices and methods for removing a predetermined shape of soft tissue from a target tissue layer, thereby leaving a matching channel with predetermined geometry and orientation in the target tissue layer, are described. The medical device comprises coaxial outer and inner elongated members extending along axis X; said outer member comprises an open distal side and a first distal part configured for sticking to said target tissue layer during forward axial movement; said inner member comprises a second distal part configured to rotate and project distally through said open distal side to cut said predetermined shape of the soft tissue from the target tissue layer and create said channel formed as a hole across the target tissue layer.

TECHNOLOGICAL FIELD

The present invention is in the medical field and relates specificallyto surgical devices, and more specifically to miniature surgicalcuttings tools.

BACKGROUND

Removing tissue from the body is solicited in various scenariosincluding for diagnosis or treatment purposes. For example, in biopsyprocedure, a sufficiently small tissue specimen is acquired in order toundergo examination outside the body. Usually, the shape of the specimenor the cavity left at the site of the removed tissue have low or noimportance, the body heals from the injury leaving apparently no traces.In another example, tissue is removed in order to create paths fordrainage of excessive liquids such as in Glaucoma condition (excessiveintra ocular pressure).

Several surgical procedures are practiced to treat Glaucoma and/orelevated intraocular pressure (IOP). Filtering surgeries are used togain access to the inner layers of the eye in order to create a drainagechannel from the anterior chamber to the external surface of the eyeunder the conjunctiva, allowing aqueous humor to seep into a bleb fromwhich it is slowly absorbed. Filtering surgeries are divided into eitherpenetrating or non-penetrating types depending upon whether anintraoperative entry into the anterior chamber occurs. Scar formation atthe site of operation may block aqueous humor circulation. Surgicaladjuvants may be used to facilitate healthy tissue regeneration and keepcreated drainage channels functional.

Trephination to create ab interno sclerostomies was reported by Brown etal (Brown R H, Lynch M G, Denham D B, et al. Internal sclerectomy withan automated trephine for advanced glaucoma. Ophthalmology 1988;95:728-734), and by SHIHADEH et al (Wisam A. Shihadeh, MD, Robert Ritch,MD, Jeffrey M. Liebmann, MD. Rescue of failed filtering blebs with abinterno trephination. Cataract Refract Surg 2006; 32:918-922), as a wayof performing filtering procedures, after failure of other proceduresdue to blocking, while maintaining the integrity of the overlyingconjunctiva at the treated site.

GENERAL DESCRIPTION

The present invention provides a novel technique for removal of tissuefrom the body. The technique of the present invention is particularlyeffective and useful in the controlled removal of soft tissue, e.g. bycreating a well-defined, timely-controlled channel inside tissue. Thetechnique of the present invention also provides for verifying thechannel's creation and its dimensions, without a need for using externalverification techniques such as imaging, by retrieving and preservingthe shape of the tissue removed. It should be noted that a “channel” asused herein means a pathway created in the tissue after removal of acorresponding tissue piece from the body. No parts, such as implant(s),are left in the body to create or maintain the integrity of the channel.Other expressions that are used interchangeably herein are “hole”,“void” and “pathway”. Specifically, the unique technique allows forcontrollably creating a channel in one or more adjacent target tissuelayers being part of a multilayered tissue structure while preservingthe one or more tissue layers covering/preceding and/or following thetarget tissue layer(s). Further, the unique technique provides the userwith on-line feedback referring the success of the channel creatingprocedure by verifying the removed tissue volume and shape. The lengthand/or the diameter, of the removed tissue (e.g. having a cylindricalshape) matches/indicates about the length and/or diameter of the createdchannel Minimizing the applied deformation on the removed tissue keepsit as close as possible to its original length and/or diameter, therebyproviding improved and better real time feedback.

It is noted that the words “tissue layer” as used herein can mean asingle tissue layer or a group of layers such as adjacent stacked layers(a multilayer) or a group of distinct layers. However, generally, thesingle tissue layer is the default meaning. Also, the “tissue layer”refers often to a tissue wall having a specific thickness and two sides(outer and inner, or proximal and distal) such that the channel/holecreated therein extends between the two sides of the tissue wall.

For example, the channel may be a channel in the sclero-corneal junctionof a subject's eye, which may be used to treat glaucoma by reducingintraocular pressure through providing fluid communication between theanterior chamber of the eye and the interface between the episclera andthe conjunctiva tissues.

In the above-described literature (Brown et al and Shihadeh et al), theAb interno trephination technique involve invasively introducing thesurgical device into the anterior chamber of the eye through an incisionmade in the cornea opposite to the site of channel creation. Thisprocedure is demanding, it depends heavily on the expertise of thesurgeon and on the ability to accurately visualize the route of thesurgical device inside the anterior chamber parallel to the iris intothe filtration angle. It is also risky to vital organs such as the irisand lens as well as the angle structures that cannot be directlyvisualized unless an additional gonioscopic lens is used. Thisintraoperative gonioscopic lens is only rarely used even by glaucomasurgeons.

In contrast, the present invention provides a safe, minimally-invasive(Ab externo) and blazingly fast (in the order of seconds),highly-effective technique. As such, the present invention provides anopportunity for combined surgery by combining several surgicaloperations, for example combining treatment of high intraocular pressureaccording to the invention, together with cataract surgery, thus savingtime and effort from both the surgeon and the patient.

Although, as described above, the present invention is advantageous inits Ab externo application, the device of the present invention can alsobe safely and effectively applied in Ab interno procedure, because aswill be further detailed below, the device includes an outer part thatfunctions as a protector that is configured to protect organs of theeye, including internal organs, such as the iris, when utilized in Abinterno configuration.

At different sites in the body, the target tissue in which the channelhas to be made underlies or precedes other tissue(s). In such asituation, the challenge is even greater because harm to the surroundingtissue(s) or adjacent should be avoided. One example is creating achannel in the sclera while keeping the conjunctiva intact. The medicaldevice of the present invention is configured, in the Ab externoapplication, to optimize the remote penetration through the outer,first, tissue (e.g., conjunctiva) followed by cutting inner, second,tissue (e.g., sclera) to form a channel, while the minimal forcepossible is applied, such that the hole created in the upper tissue(conjunctiva) heals almost immediately leaving no traces. On the otherhand, in the Ab interno application, the device, while being actuallyinserted into the anterior chamber of the eye, its construction and wayof action ensure that no harm is caused to other organs, including theouter conjunctiva, while it creates a channel in the sclera tissue frominside.

Further, the medical device of the present invention is configured foreasy automatic or semi-automatic operation, relieving burden fromsurgeon and providing him continuous feedback over the whole surgicalprocedure. The technique of the present invention aids the surgeon insafe positioning of the device inside the tissue to be cut while stillallowing him/her control over the channel's three-dimensionalorientation.

Moreover, the device of the present invention may incorporateauthentication or validation features by retaining form/specimen oftissue removed from the body during the channel creation. The shape ofthe cutting tool of the device also provides enhanced trapping of theremoved tissue within the cutting tool and prevents or minimizes thechances of leaving the removed tissue within the tissue wall such as theeye wall.

The channel created by the technique of the present invention isadvantageous, for example in comparison to other techniques that leaveimplant(s) inside the tissue so to insure the drainage of fluid, becausenothing is left in the tissue, except for the created void/hole/channelextending between the two side walls of the specific target tissue layeror multilayer, as the case may be. In other words, the created channelis a hole through the tissue with no artificial tube/shunt left insidethe target tissue at all. Therefore, the created channel can be dynamicacting as a pressure regulator, i.e. it can regulate its drainagecapacity by changing its size based on the pressure acting on its bothends. When the pressure gradient increases the channel opens/increasesits size accordingly, and when the pressure gradient decreases thechannel closes/decreases its size accordingly.

The range of sizes of the channel can be controlled by the geometry andsize of the device that creates the channel. In the specific example ofcreating a channel in the eye wall, to treat elevated IOP for example,the present invention is advantageous in achieving the channel creationand verification in the micro scale, as the desired dimensions of thedrainage channel are typically about 0.1-0.2 mm in diameter and 1-1.5 mmin length, supposing a substantially cylindrical shape for the channeland the matching removed tissue. The present invention accomplishes thetargets above in the micro level while overcoming the limitations of thecurrently available techniques. Inter alia, available techniques may beused to produce tools having tissue receiving cavities of up to about0.5 mm length with the required above-mentioned diameter. However, thisis not suitable for creating a substantially cylindrical channel withinthe eye wall that has a 1.5 mm length. The technique of the presentinvention enables creating cutting tools with micro-scale desireddimensions in diameter and length, thereby enabling to preserve theshape of the removed tissue to be used for verification of the channelcreation.

Generally, the medical device of the present invention is configured tooperate in three distinct phases, a positioning phase characterized byan essentially linear advancement of the device along its linearlongitudinal axis through one or more tissue layers until reaching thetarget tissue and stabilizing there inside the target tissue by ananchoring/sticking portion of an outer part of the device, a channelingphase during which an inner rotatable cutting tool of the device isrotated around its linear longitudinal rotation axis and then advancedto project from the outer part of the device and progress inside thetarget tissue to cut tissue of the target tissue and create the channelwith the desired dimensions (diameter, cross-section area, length . . .), and a withdrawal phase in which the inner rotatable cutting tool iswithdrawn from the target tissue into the outer part of the device andthe whole device is retracted from the body. The withdrawal phase may bewith or without rotation of the inner rotatable cutting tool depending,inter alia, on the tissue characteristics (kind, stiffness, region inthe body), the time of operation and the desired channel shape.Typically, the outer part does not rotate during any of the phases andit only moves straight forwards and backwards on the linear longitudinalaxis of the device. Generally, the outer part functions as a protectiveshaft, that protects the surrounding tissue during advancement of thedevice until reaching the target tissue, and as a stabilizing part suchthat its front (distal) portion is inserted/anchored/stuck in the targettissue to enable stable activation and performance of the innerrotatable cutting tool during the channeling phase.

Thus according to a broad aspect of the invention, there is provided amedical device for removing a predetermined shape of soft tissue from atarget tissue layer thereby leaving a matching channel withpredetermined geometry and orientation between two side walls of thetarget tissue layer, the device comprises coaxial outer and innerelongated members extending along axis X;

said outer member comprises an open distal side and a first distal partconfigured for sticking to said target tissue layer (or multilayer),during forward axial movement;

said inner member comprises a second distal part configured to rotateand project distally through said open distal side to said predeterminedshape of the soft tissue from the target tissue layer and create saidchannel formed as a hole through the target tissue layer or multilayer.

In some embodiments, the first distal part is configured for penetratingat least one other tissue layer preceding the target tissue layer duringthe forward axial movement.

In some embodiments, the first distal part comprises a tissue piercingtip at its distal end configured and operable to penetrate said at leastone other tissue layer and said target tissue layers and a proximalportion at its proximal side configured and operable to penetrate saidat least one other tissue layer and to stop at said target tissue layer,thereby sticking said outer member in the target tissue layer.

In some embodiments, said first distal part has a mid-portion betweensaid tip and said proximal portion having a shape and an orientationthat complement a shape and an orientation of said second tissue layer.

In some embodiments, the first distal part has a predefined length suchthat said tip does not exit distally from said target tissue layer.

In some embodiments, the proximal portion is a rim of said outer member,formed by cutting a section of wall of the outer member along said axisX.

In some embodiments, the inner member is fixedly attached to and housedwithin said outer member during said forward axial movement of the outermember.

In some embodiments, the outer member is manually moved during saidforward axial movement until its said sticking in the second tissuelayer.

In some embodiments, the inner member, while rotating, is manually movedalong said axis X to create the channel.

In some embodiments, the device comprises a constant-force movingmechanism configured and operable to move said inner member, whilerotating, along said axis X under a constant force. In some otherembodiments, the device comprises a constant rate moving mechanismconfigured and operable to move said inner member, while rotating, alongsaid axis X with a constant rate.

In some embodiments, the device comprises an electric motor configuredand operable for axially moving and/or rotating said inner member.

In some embodiments, the device comprises a cavity for collecting tissuecut from said target tissue layer during creation of said channel. Insome embodiments, the cavity is located within said inner member. Insome embodiments, the cavity is located in a space between said innerand outer members.

In some embodiments, the second distal part of said inner member is openat its distal end and comprises a round cutting edge configured toattach to and cut soft tissue while rotating. The inner member maycomprise a chamber for retaining a full shape of tissue cut from saidsecond tissue layer during creation of said channel.

In some embodiments, the inner member comprises:

-   -   an elongated round body extending along a longitudinal axis and        having a uniform outer diameter at a proximal side thereof,    -   a cutting portion at a distal side of the elongated body,        comprising at a distal end thereof a round cutting edge of a        first diameter being smaller than said outer diameter and a        distally and continuously decreasing outer diameter, and    -   a cavity extending along the longitudinal axis inside the        cutting tool from said cutting portion, the cavity having        dimensions matching said soft tissue shape,    -   wherein said tissue shape is cylindrical and has a length of        about 1.5 mm and a diameter of between about 0.1 mm and about        0.2 mm.

In some embodiments, the inner member comprises:

-   -   an elongated round body extending along a longitudinal axis and        having a uniform outer diameter at a proximal side thereof,    -   a cutting portion at a distal side of the elongated body,        comprising at a distal end thereof a round cutting edge of a        first diameter being smaller than said outer diameter and a        distally and continuously decreasing outer diameter, and    -   a cavity extending along the longitudinal axis inside the        cutting tool from said cutting portion, the cavity having a        length of at least the length of the removed tissue,    -   wherein said cavity has a cavity diameter smaller than said        first diameter at a distal end of the cavity and which increases        continuously towards a proximal end of the cavity.

In some embodiments, the inner member comprises:

-   -   an elongated round body extending along a longitudinal axis and        having a uniform outer diameter at a proximal side thereof,    -   a cutting portion at a distal side of the elongated body,        comprising at a distal end thereof a round cutting edge of a        first diameter being smaller than said outer diameter and a        distally and continuously decreasing diameter, and    -   a cavity extending along the longitudinal axis inside the        cutting tool from said cutting portion, the cavity having a        length of at least the length of the removed tissue,    -   wherein said cavity has a constant cavity diameter being equal        to said first diameter, and wherein said first diameter is        between about 0.1 mm to about 0.2 mm.

In some embodiments, the inner member comprises a tissue trappercomprising a slit formed in a wall of the body of the inner member alongat least part of said cavity. In some embodiments, the slit is formed bytangential cutting of the wall of the body of the inner member, saiddevice thereby further comprising an outer cavity located between theinner and outer members. In some embodiments, the slit is formed byradial cutting of the wall of the inner member.

In some embodiments, the second distal part of said inner member isconfigured as a drill bit configured for removing soft tissue.

In some embodiments, the rotating of said second distal part comprisesclockwise and anti-clockwise reciprocal movement.

In some embodiments, the tissue piercing tip is configured as a lancet.

In some embodiments, the first distal part of the outer member is formedby cutting the outer member in the direction of the axis X along acurved line chosen to provide smooth penetration, at a distal segment ofthe first distal part, with increasing resistance-to-progression force,at a proximal segment of the first distal part.

In some embodiments, the at least one other tissue layer comprises theconjunctiva and/or the tenon and said target tissue layer is theepisclera and/or the sclera and/or the cornea of an eye.

In some embodiments, the predetermined geometry of the channel isselected to enable pressure regulation of a treated eye over apredetermined time period.

According to yet another broad aspect of the invention, there isprovided a method for producing a cutting tool used in cutting softtissue, the cutting tool comprising a distal cutting portion having at adistal end thereof a round cutting edge of a first diameter and a cavityextending for a predetermined length along a longitudinal axis of thecutting tool from said cutting portion and comprising a cavity diameterbeing either constant or increasing proximally along the predeterminedlength, the method comprising:

-   -   providing a tool comprising at a distal side thereof a hollow        cylinder having uniform outer and inner diameters and extending        along at least said predetermined length, wherein said inner        diameter is larger than said first diameter,    -   shaping a distal portion of the hollow cylinder with a        predetermined pattern such that both said inner and outer        diameters decrease towards a distal end of the hollow cylinder        and such that said first diameter is larger than said inner        diameter and is smaller than said outer diameter at the distal        end, and    -   removing a slice of the hollow cylinder along said distal        portion, such that the inner diameter at the distal end is        substantially equal to said first diameter and the inner        diameter at a proximal end of the distal portion is        substantially equal to said cavity diameter.

In some embodiments, said shaping of the distal portion is carried outby swaging and/or spinning technique(s).

In some embodiments, said shaping of the distal portion is carried outby tapering technique.

In some embodiments, said predetermined pattern is linear.

In some embodiments, said predetermined pattern is non-linear.

In some embodiments, said cavity diameter is equal to said firstdiameter.

In some embodiments, the method further comprising: sharpening saidround cutting edge from an internal side of the cutting portion, therebyproviding that the cavity diameter at a proximal end of the cuttingportion being smaller than the first diameter. In some embodiments, saidcavity diameter increases proximally.

In some embodiments, the method further comprising coating an innersurface of said cavity with a friction-lowering composition.

In some embodiments, said predetermined length is at least 1.5 mm.

In some embodiments, said cavity diameter at a proximal side of thecavity is between 0.1 mm and 0.2 mm.

In some embodiments, said uniform outer and inner diameters of thehollow cylinder are about 0.3 mm and 0.16 mm respectively.

In some embodiments, after shaping, said outer and inner diameters ofthe hollow cylinder at the distal end are about 0.27 mm and 0.13 mmrespectively.

In some embodiments, said distal portion of the hollow cylinder has alength along the longitudinal axis of between about 1 mm to about 2 mm.

According to yet another aspect of the present invention, there isprovided a cutting tool for removing a predetermined shape of softtissue while revolving and progressing, thereby leaving a matchingchannel between two walls of the soft tissue, the cutting tool beingproduced according to the method described above.

According to yet another broad aspect of the invention there is provideda method for creating a channel with predetermined geometry in a targettissue layer, the channel being formed as a hole extending between twoside walls of the tissue layer, the method comprising:

providing a device comprising coaxial outer member comprising a firstdistal part configured for sticking to said tissue layer during forwardaxial movement and inner member comprising a second distal partconfigured to cut and remove tissue to thereby create said channel;

positioning said device at the target tissue layer by progressing thedevice along an axis X while said inner member is located inside saidouter member until reaching said target tissue layer where the firstdistal part of the outer member is pushed into the target tissue suchthat at least a distal portion of the distal part is stuck inside thetarget tissue layer;

creating said channel by rotating and projecting said second distal partfrom said outer member to thereby cut and remove tissue from said targettissue layer and store the removed tissue in the device;

retracting said second distal part proximally out of said target tissuelayer and into the inside of the outer member; and

pulling the first distal part proximally out of said target tissue layerand withdrawing the device out of the body substantially along the axisX.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosedherein and to exemplify how it may be carried out in practice,embodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawings, in which:

FIGS. 1A-1B illustrate a non-limiting exemplary embodiment of a deviceaccording to the invention;

FIGS. 2A-2B illustrate another non-limiting exemplary embodiment of adevice according to the invention;

FIGS. 3A-3E exemplify a non-limiting technique for creating a channel insoft tissue according to the invention;

FIGS. 3F-3I exemplify another non-limiting technique for creating achannel in soft tissue according to the invention;

FIGS. 4A-4D illustrate non-limiting examples of a part of a deviceaccording to exemplary embodiments of the invention;

FIGS. 5A-5D3 illustrate non-limiting examples of a part of a deviceaccording to the invention;

FIGS. 5E1-5E7—illustrate one non-limiting scenario of creating a channelin soft tissue and specifically in the eye wall;

FIGS. 5F-5G4 illustrate non-limiting examples of a device and methodsfor producing the device according to exemplary embodiments of theinvention;

FIGS. 6A-6D illustrate a non-limiting example of a manual movementmechanism according to the invention;

FIGS. 7A-7D illustrate another non-limiting example of manual movementmechanism according to the invention;

FIGS. 8A-8D illustrate yet another non-limiting example of manualmovement mechanism according to the invention;

FIGS. 9A-9E illustrate a non-limiting example of automatic movementmechanism according to the invention; and

FIGS. 10A-10D illustrate another non-limiting example of automaticmovement mechanism according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention provides a technique for creating a well-definedchannel in a soft tissue. In one aspect, a medical device for removing apredetermined shape of soft tissue from a target tissue layer (or afirst group of target tissue layers) thereby leaving amatching/corresponding channel with predetermined geometry and/ororientation through/between two side walls of the target tissue layer isprovided. In some embodiments, such a device can be particularly usefulin creating a drainage channel along the whole thickness of theepisclera and/or sclera and/or cornea tissue (which will be generallyreferred to herein, for simplicity, as the sclera), of the eye tothereby treat excessive intraocular pressure. The sclera is covered bythe conjunctiva and tenon tissues, such that approaching the sclera fromoutside requires penetrating the conjunctiva and the tenon. Therefore,the device may be also configured to penetrate through theconjunctiva/tenon before reaching the sclera.

Reference is made to FIGS. 1A and 1B showing a specific, non-limiting,example of a medical device 100 according to some embodiments of thepresent invention.

The medical device 100 is configured for and capable of penetratingthrough first, upper, tissue layer(s) and creating a channel withpredetermined geometry through a consecutive second, lower, targettissue layer. The device 100 includes coaxial outer and inner members,110 and 120 respectively, extending along axis X, for creating thechannel in the target tissue, and possibly penetrating the tissuelayer(s) preceding the target tissue layer. The axis X is typically alongitudinal straight axis. The coaxial outer and inner members 110 and120 are usually made from a hard, tough, material and are thereforerigid and do not bend when pushed/inserted/progressed through at leastsoft tissue. The coaxial outer and inner members 110 and 120 aremounted, at a proximal side 114P thereof, on a handle/gripping unit 150by which the user holds/grips the device 100 and operates it.

The outer member 110 includes an open distal side 112D, a first distalpart 112, and a first proximal elongated part 114. It is noted that therelative expressions “proximal” and “distal” as used herein, definerelative orientation with respect to the user, such that “proximal”denotes the close side to the user and “distal” denotes the far sidefrom the user. The outer member 110 is configured to move axially alongthe axis X to thereby penetrate soft tissue by its first distal part112. The axial movement of the outer member 110 is achieved by usermanual operation. As it is manually operated by the user, the outermember 110 can be fixedly/firmly attached, at the proximal side 114P, tothe handle 150. Alternatively, it can be configured for manual slidingby the user along axis X while not being firmly attached to the handle150. Details about the moving mechanism are described herein furtherbelow.

The first distal part 112 is configured for penetrating and passingthrough the tissue layer(s) preceding the target tissue layer, if any,during forward axial movement, and therefore it includes a tissuepiercing tip 116, at the distal end of the first distal part 112, thatenables the penetration. It is noted that, as the forward axial movementis manually controlled, the penetration of the preceding tissuelayer(s), such as the relatively thin conjunctiva, is enabled by themanual pushing force applied by the user and which can be furtherfacilitated by the manual lifting/pulling of the conjunctiva outwardlytowards the user. The first distal part 112 is also configured to piercethe target, typically thicker, tissue layer, and stick into the targettissue layer so as to position the device inside the target tissue inwhich the channel is to be created, and provide the user with a pivotalpoint to define the three dimensional orientation of the channel. Inaddition to its plain name, the first distal part 112 is interchangeablycalled herein as “sticking part”, “stabilizing part” or “anchoringpart”. It should be understood that while the first distal part 112enters into the target tissue and sticks/anchors therein, it can bewithdrawn backwardly by the application of a minimal force and withoutcausing damage to the surrounding tissue. Sticking and/or anchoring asused herein do not mean a permanent state but rather a temporal,transitional state of the position of the first distal part, that givesthe user a stable pivotal point of action.

The tissue piercing tip 116, formed at the most distal part of the firstdistal part 112, can be configured according to the known in the art,e.g. as done with conventional medical needles. Accordingly, the tissuepiercing tip 116 can include, for example, a beveled lancet structure.Yet, it can have other configurations, as will be further describedbelow with reference to FIGS. 4A to 4D.

The first proximal elongated part 114 is hollow, e.g. a hollow tube,enclosing and housing the inner member 120 there inside. Typically, thefirst proximal elongated part 114 has a cylindrical shape with acircular (round) or substantially circular transverse outer crosssection. The first proximal elongated part 114 is configured topenetrate soft tissue smoothly and easily with minimum force, thereforeit can have circular outer cross section and can be provided with asmooth (polished) outer surface to minimize friction during penetrationinto tissue. The inner cross section of the first proximal elongatedpart 114 is circular or has other shape that matches the outer surfaceof the inner member 120 enclosed therein.

The inner member 120 includes a second distal part 122 and a secondproximal elongated part 124. The second distal part 122 is configured toproject distally through the open distal side 112D, approaching thetarget tissue while rotating, to thereby cut a predetermined shape ofthe target tissue and create the channel with the predetermined geometryand orientation in the target tissue, while the first distal part 112 issubstantially positioned inside the target tissue as described above andas will be further exemplified below with reference to FIGS. 3A to 3I.In general, the second distal part 122, at its distal end, is configuredto provide effective attachment to the target tissue and to cut thetarget tissue while rotating. To this end, the distal end of the seconddistal part 122 can be provided with a cutting edge, a punchingmechanism and the like, as will be further described below.

Generally, the device 100 includes a cavity/chamber 126 configured tocollect the removed tissue therein, such that no tissue is left in thebody. In some embodiments, the cavity/chamber is located inside thesecond proximal elongated part 124, as exemplified in FIG. 1B. In someother embodiments, the cavity/chamber 126 can be located in a spacebetween the outer and inner members 110 and 120.

The device 100, including the handle 150 may be configured for singleuse, being disposable, therefore enhancing and maintaining safety andsterility of the device. The handle 150 can be configured as describedin PCT/IL2016/051063 assigned to the assignee of the present invention.

The moving mechanism 140 is configured to enable axial movement of theouter member 110, forwards (distally) and backwards (proximally), andboth axial and rotational movement of the inner member 120. The movingmechanism 140 can have manual (by the user) and/or automatic (by the useof mechanical and/or electrical means, such as a spring and/or a motor)operational modes for each of the movements it is capable of. Therotational movement of the inner member 120 can be in full or partialcircles or rounds, clockwise and/or anticlockwise, and/or in reciprocalmovement.

The construction and dimensions of the device can be costumed to matchthe application, the tissue properties, and anatomy and morphology ofthe site of body in which the channel is created.

For example, if used to create a drainage channel in the human eye, thedimensions of the device can be as follows:

The external diameter of the outer member is chosen to enable smooth andsafe penetration into and withdrawal from tissue, while maintaining aminimal strength such that it does not break in the tissue duringoperation. It can be about 0.4-1.2 mm.

The overall length of the outer member is chosen to enable easy and safeaccess to the surgery site. It can be about 8-30 mm.

The length of the first distal part of the outer member can be chosen toenable insertion/sticking/anchoring of the first distal part into thesecond tissue, i.e. the sclera in this instance, while assuring that thefirst distal part does not protrude distally from the sclera, thusminimizing or cancelling invasive entrance into the anterior chamber ofthe eye. It can be about 0.5-3 mm.

The external diameter of the inner member is chosen to create thepredetermined geometry of the channel, while maintaining a minimalstrength such that it does not break in the tissue during operation. Itcan be about 0.2-0.5 mm.

The overall length of the inner member is chosen to enable itsconnection to a moving mechanism at the proximal side while providingsufficient forward distance to create the desired channel length. It canbe about 15-40 mm.

The length of the second distal part of the inner member depends on thesecond distal part's specific construction that insures the channelcreation.

During the channel creation, the inner member protrudes/projects fromthe outer member by about 1-4 mm.

The inner member's rotation can be in the range of about 1-10,000 rpm.And, the penetration force is about 0.2-10 Newton.

The resulting channel's diameter would be about 0.1-0.5 mm.

Reference is made to FIGS. 2A and 2B. Throughout the text, functionalparts which have the same functionality, have the same numbers withdifference of one hundred duplicates. For example, the number 210denotes an outer member and the number 220 denotes an inner member, bothconfigured as at least having the features described above with respectto outer member 110 and inner member 120, with possibly additionalfeatures. In the following various non-limiting embodiments of thedevice, including its outer and inner members and its moving mechanismwill be exemplified. It should be understood, that any combination ofone outer member, one inner member and one moving mechanism is equallypossible. The shown or described specific examples should not limit thebroad aspects of the invention.

FIGS. 2A and 2B exemplify a non-limiting example of the device 200 ofthe invention. In the figures, an outer member 210 and inner member 220of the device 200 are shown. The outer member 210 and the inner member220 are configured and operable at least as the outer member 110 andinner member 120 described above. FIG. 2A (as well as FIG. 1A)illustrates the device during the positioning phase, i.e. duringinserting the device through the first and second (target) consecutivetissues, in which the outer member 210 leads the device into itsposition inside the second tissue to be channeled, and the inner member220 (as well as 110 in FIG. 1A) is housed entirely in the outer member210. FIG. 2B (as well as FIG. 1B) illustrates the device during thechanneling phase, i.e. during creation of the channel by the rotationaland forward movement(s), projection, of the inner member 220. As shown,the first distal part 212 of the outer member 210 includes a piercingportion/tip 216 at its most distal side, being configured as describedabove and operable to pierce and penetrate through tissue layer(s)preceding the target tissue, and to pierce, without fully penetrating,the target tissue layer. In addition, the first distal part 212 includesa portion 212P at its proximal side configured and operable to pierceand penetrate the tissue layer(s) preceding the target tissue layer andto stop at the second (target) tissue layer, i.e. the portion 212Pprevents the outer member 210 from excessively penetrating the second(target) tissue in which the channel is created thereby sticking theouter member 210, by its distal piercing portion 216, in the targettissue layer. The portion 212P is interchangeably called herein as“stopping portion” or “stopper”.

In the described example, the stopper 212P is an integral portion of theouter member 210 formed by a rim of the transverse, round, cross sectionof the outer member 210 by cutting a section of wall of the outer member210 substantially along the axis X. Specifically, the section cut is awall of the cylinder of the outer member 210, e.g. half of the cylinderof the outer member between its most distal end and up to a proximalpoint along the outer member. The length of the wall section cut alongaxis X defines the length of the first distal portion 212 and the latterdefines the extent of sticking the outer member 210 into the targettissue such that the distal end of the piercing tip 216 does notprotrude/exit distally from the target tissue layer.

Reference is made to FIGS. 3A to 3I exemplifying non-limiting techniquesfor creating a channel in soft tissue by using the medical device of theinvention. The described example relates to creating a channel in thesclera tissue of the eye. However, as has already been said, theinvention is not limited to this application and can be practiced atother regions in the body where creation of a controlled channel in atissue layer preceding/beneath other tissue layer(s) is needed.Specifically, the invention enables channel creation at a region in thebody which needs a clear and defined stopping/localization/stabilizationfeature of the device therein because the region cannot provide thisfeature; such a region is the soft tissue. The example described inFIGS. 3A to 3E relates to Ab externo procedure where the deviceapproaches the sclera tissue from outside. A human eye 360 is shown,where a channel should be created at the region of the sclera-cornealjunction 362. The created channel will controllably connect between theanterior chamber 364 of the eye and the sub conjunctival space/zone andhence allow the extra fluid accumulated in the anterior chamber to exitand by this reduce the intraocular pressure. As has been describedearlier, the channel size can be controlled by providing a device withspecific geometrical dimensions. Also, when used for treating excessivepressure, the size of the created channel is determined based on themagnitude of excessive pressure that should be treated. Higher pressurerequires bigger channel and vice versa. The created channel insureseffective regulation of pressure such that it expands or contractsbetween controlled sizes based on the pressure gradient across thechannel, i.e. the pressure difference between inside and outside theeye.

As shown in FIG. 3A, the device 300 approaches the eye from outsidewhere it encounters the outer tissue layer that includes the conjunctivaand/or tenon tissues (366 in FIG. 3B) by the outer member 310, andprecisely by the first distal part 312 of the outer member 310. Theouter member 310 pierces and penetrates the conjunctiva and/or tenonwhen it is advanced forwardly, typically manually, by the surgeon.

As shown in FIG. 3B, after or while the device passes the conjunctivaand tenon 366, the surgeon can pull the conjunctiva 366, and possiblyalso the tenon, outwardly by the help of a suitable tool held in hisother hand. The conjunctiva tissue, and possibly also the tenon, nowwraps the outer member 310 at the first proximal elongated part 314.This saves the conjunctiva and/or tenon by preventing them from cominginto contact with the inner member which will be rotated and advanced tocut and remove sclera tissue. The tissue piercing tip 316 of the outermember 310 now contacts the sclera tissue 368.

As shown in FIG. 3C, the outer member 310 is further advanced forwardly,manually, as described above, such that the piercing tip 316 penetratesthe sclera tissue 368. The device, by the first distal part 312 of itsouter member 310, is stuck in (anchored) and stabilized temporarily inthe sclera tissue 368. During advancement inside the sclera tissue 368,the resistance-to-progression increases and is given as a feedback tothe surgeon when he/she manually advances the device. In the case thedevice is configured with the stopper 312P, as shown in this specificexample, the device 300 comes to a hard stop because the stopper 312Pprovides significant increase in resistance-to-progression force on theouter member 310 and prevents the additional penetration/progressioninside the sclera tissue 368.

It is appreciated that FIGS. 3A to 3C illustrate the positioning phaseof the device 300 as a preparation for the channeling phase. It is alsoappreciated, that during the positioning phase, no relative motionbetween the outer and inner member occurs. Generally, the inner memberis hidden inside and fixedly attached to the outer member during theaxial movement of the outer member, no matter how the axial movement ofthe outer member is executed, whether the axial movement includes manualdisplacement of the outer member by the surgeon relative to the handle,or whether the outer member is fixedly attached to the handle such thatthe axial movement of the outer member is generated by manual axialmovement of the handle by the surgeon.

At this point, as shown in FIG. 3D and while the outer member 310protects the conjunctiva tissue, the inner member 320 is rotated, eithermechanically or electrically by a dedicated motor as described above andwill be further exemplified below, and is advanced by the applied movingmechanism forwardly such that it contacts and attaches to the scleratissue 368 and starts with drilling and creating the channel. Theadvancement distance of the rotating inner member can be configured bythe moving mechanism such that the distal end of the inner member 320does not protrude significantly into the anterior chamber of the eye toavoid causing harm to the internal side of the eye. The inner member 320is then retracted backwardly (not shown), either rotating or notdepending on its configuration, as will be described further below,until it is back in its secured position inside the outer member 310,and the latter is pulled out from the sclera and conjunctiva tissues bythe surgeon. The conjunctival tissue recovers almost immediately and thehole therein, formed by the outer member only, closes. Moreover, asduring the positioning phase the surgeon pulls the conjunctivaoutwardly, then after releasing the conjunctiva the hole in theconjunctiva will be displaced with respect to the channel in the sclera.As the conjunctiva attaches back to the sclera, the risk of eye collapsedue to excessive fluid exiting the eye is prevented.

FIG. 3E illustrates the created channel 370 after the device is pulledoutside the eye. The aqueous humor (the fluid in the anterior chamber)starts to exit the anterior chamber towards the sub-conjunctival space,such that a bleb 372 is formed under the conjunctiva and above thesclera, and the fluid is reabsorbed in the blood vessels at the vicinitythereof.

Reference is now made to FIGS. 3F to 3I exemplifying anothernon-limiting technique for creating a channel in soft tissue by usingthe medical device of the invention. The described example relates tocreating a channel in the sclera tissue of the eye in Ab internoprocedure by approaching the sclera tissue from inside of the eye. Ashas been mentioned above, the device of the invention is advantageous inthat it can be used in either Ab externo or Ab interno procedures. Forsimplicity of presentation, every feature which is not referenced in thefigures is assumed to be the same as in FIGS. 3A to 3E. The human eye isshown, where a channel should be created at the region of thesclera-corneal junction 362, as depicted in FIG. 3F. As described above,the created channel will controllably connect between the anteriorchamber of the eye and the sub conjunctival space/zone and hence allowthe extra fluid accumulated in the anterior chamber to exit and by thisreduce the intraocular pressure. The properties of the channel,including its size and geometry, can be as has been described earlierwith reference to FIGS. 3A to 3E. As shown in FIG. 3F, the device 300approaches the eye from outside and is to be inserted into the anteriorchamber 364 of the eye through an opening 374 created beforehand inclear cornea at the opposite side to where the channel is to be created.The opening 374 can be achieved by conventional means known in the artsuch as a stylet blade. The device is inserted with respect to the eyein an orientation which is opposite to the orientation described inFIGS. 3A to 3E relating to the Ab externo procedure. In other words, thetissue sharp tip of the outer member is now closer to the internal sideof the eye, whereas it was farther away in the Ab externo procedure (asshown in FIG. 3A). By this, the first distal portion beveled shape andorientation will complement the shape and orientation of the sclera atthe contact region 362.

The device is inserted into the anterior chamber and is pushed manuallyby the surgeon, while passing above the iris 376, until it contacts thesclera tissue at the sclera-corneal junction 362 from inside.

As appreciated from FIG. 3G, after the surgeon feels the contact,another pushing force is applied manually in the forward direction, suchthat the outer member 310 pierces and penetrates the sclera (from theinside). The device, by the first distal part 312 of its outer member310, is stuck in (anchored) and stabilized temporarily in the scleratissue. As described above, during advancement inside the sclera tissue,the resistance-to-progression increases and is given as a feedback tothe surgeon when he/she manually advances the device. In the case thedevice is configured with the stopper 312P, as shown in this specificexample, the device comes to a hard stop because the stopper providessignificant increase in resistance-to-progression force on the outermember and prevents the additional penetration/progression inside thesclera tissue. As also described above, the preconfigured length of thefirst distal portion of the outer member insures that the piercing tipdoes not exit the sclera from the other (here external) side, such thatthe conjunctiva or other covering tissue is not torn or pierced by theouter member.

It is appreciated that FIGS. 3F and 3G illustrate the positioning phaseof the device 300 as a preparation for the channeling phase. It is alsoappreciated, that during the positioning phase, no relative motionbetween the outer and inner member occurs. Generally, the inner memberis hidden inside and fixedly attached to the outer member during theaxial movement of the outer member, no matter how the axial movement ofthe outer member is executed, whether the axial movement includes manualdisplacement of the outer member by the surgeon relative to the handle,or whether the outer member is fixedly attached to the handle such thatthe axial movement of the outer member is generated by manual axialmovement of the handle by the surgeon.

As shown in FIG. 3H, while or after the outer member is anchored intothe sclera tissue, the surgeon can pull and lift the conjunctiva 366,and possibly also the tenon, outwardly in a direction 378 by the help ofa suitable tool held in his other hand. This saves the conjunctivaand/or tenon by preventing them from coming into contact with the innermember which will be rotated and advanced to cut and remove scleratissue. The inner member is rotated, either mechanically or electricallyby a dedicated motor as described above and is advanced by the appliedmoving mechanism forwardly such that it contacts and attaches to thesclera tissue and starts with drilling and creating the channel. Theadvancement distance of the rotating inner member can be configured bythe moving mechanism such that the distal end of the inner member doesnot protrude significantly outside the sclera tissue to avoid causingharm to the conjunctiva and/or tenon tissues. While the inner memberrotates to cut and remove tissue from the sclera, the outer member,which is stabilized by its anchor to the sclera tissue, is stationary,it does not or hardly moves, thus preserving the internal organs, suchas the iris, from any damage that may have been caused by the rotatinginner member. Further, its anchoring to the sclera minimizes anyaccidental pulling of the rotating inner member from the sclera,something which may otherwise have adverse consequences on the internalorgans of the eye. After creating the channel, the inner member isretracted backwardly (not shown), either rotating or not depending onits configuration, as will be described further below, until it is backin its secured position inside the outer member, and the device ispulled backwardly out from the anterior chamber and out of the eyethrough the opening 374 which can be treated by suitable medicines inorder to heal and close almost immediately.

FIG. 3I illustrates the created channel after the device is pulledoutside the eye. The aqueous humor (the fluid in the anterior chamber)starts to exit the anterior chamber towards the sub-conjunctival space,such that a bleb 372B is formed under the conjunctiva and above thesclera, and the fluid is reabsorbed in the blood vessels at the vicinitythereof.

Reference is made to FIGS. 4A to 4D showing various non-limitingexamples of the outer member of the device according to somenon-limiting embodiments of the invention. The figures are illustrativeonly and are not presented in a full scale. Specifically, the figuresshow different non-limiting configurations of the first distal portionof the outer member. Generally, the shape and/or orientation of thefirst distal part can be chosen to complement the shape and/ororientation of the target tissue, such that bettercoupling/attachment/adherence/anchoring between the outer member and thetarget tissue is achieved.

FIG. 4A shows a known shape of cannula end used in medical needles. Thisis a common point cannula end known as flat bevel point. Thisconfiguration can be used as the first distal part 412A of the outermember 410A.

FIG. 4B also shows a known shape of cannula end used in medical needles.This is a common point cannula end known as lancet bevel point. Thisconfiguration can be used as the first distal part 412B of the outermember 410B.

FIG. 4C shows a special non-limiting example of a first distal part 412Cof an outer member 410C according to the invention. Similarconfiguration to FIG. 4C is also shown in FIGS. 2A and 2B. The firstdistal part 412C includes a tissue piercing tip 416C configured as alancet bevel point and a stopping portion 412PC formed by the rim of theouter member 410C which is obtained by cutting a section of the wall ofthe outer member 410C along its longitudinal axis. In some exemplary,non-limiting, embodiments, half of the wall (e.g. half of cylinder) iscut.

FIG. 4D shows another special non-limiting example of a first distalpart 412D of an outer member 410D according to the invention. The firstdistal part 412D includes a tissue piercing tip 416D and a stoppingportion 412PD both obtained by cutting the outer member 410D in thedirection of the longitudinal axis along a curved line. The curved linecan be chosen to provide smooth transition along the first distal partenabling smooth penetration with increasing resistance-to progressionforce. The curved line is usually configured as a smooth, continuousline with constant or variable slope (its derivative trend is alwayspositive or always negative, though not necessarily constant), althoughother non-continuous behavior can be used. For example, the curved linecan be a combination of two or more line segments, among which some arecurved and/or straight. Specifically, the piercing portion can beconfigured as a curved line while the stopping portion can be configuredas a straight line, e.g. in the direction of the transverse crosssection of the inner member. In some embodiments, such a smooth curvedline can follow a circular, elliptical, semi-circular or semi-ellipticalpath, e.g. can be part of a circle's or an ellipse's circumference. Inthe example shown, an elliptical curve is presented, such that theelliptical major axis lies in the direction of the longitudinal axis ofthe outer member and the elliptical minor axis is in the orthogonaldirection (across the outer member). In this instance, the major axisdefines the length of the first distal part, and the minor axis (or,more specifically the relation between major and minor axes) defines thelevel of resistance-to-progression of the stopping portion 412PD. Itshould be understood, that the above-described example relates toformation of the curved line, forming the piercing tip/stopper, alongthe longitudinal axis direction, from a single direction (2D forming),while any other shaping combination in 3D is also possible.

As has been clarified above, any configuration of the outer member canbe used with any configuration of the inner member. Also, it should benoted that all the examples presented here are by no means limiting andthe invention can be practiced with other specific suitableconfigurations.

The inner member is configured, as described above, for attachingeffectively to the second tissue (in which the channel is formed) andfor cutting a well-defined geometrical shape of the tissue, both whilerotating and advancing distally. In some embodiments, the inner memberis configured for storing the cut tissue in its intact form, thusproviding a validation and authentication to the created channel. Inaddition, storing the cut tissue inside the inner member (in the secondproximal elongated part) serves in protecting the eye from suddencollapse by blocking the outflow of aqueous humor from the anteriorchamber during the channel creation and/or when the device is pulledoutwardly from the eye.

Reference is made to FIGS. 5A-5D showing non-limiting examples of theinner member of the device according to some non-limiting exemplaryembodiments of the invention. The different examples can bedistinguished by the specific channel creating application, includingthe specific dimensions of the channel which is affected by its purposeand its location in the body. Specifically, some of the describedexamples may be more suitable than others for the application ofcreating a channel in the eye wall for treating elevated IOP.

FIG. 5A illustrates an inner member 520A having a second distal part522A configured to attach to tissue and cut tissue, while rotating andprogressing distally, and to guide the inner member through the tissue,e.g. towards the anterior chamber of the eye. The inner member alsoincludes a second proximal elongated part 524A that includes anelongated chamber/cavity (not shown) configured to receive therein thetissue being removed. The outer diameter of the inner member shouldpreferably match the inner diameter of the outer member such that nospace is left there between. The shape of the chamber/cavity preferablymatches the shape of the cut tissue. In action, the inner memberapproaches the tissue while rotating (at least the second distal part),so that the rotation creates desired attachment of the inner member tothe tissue and enables start of the piercing and cutting. Generally, thesecond distal part 522A has at the distal end a round cutting edge522EA, typically of a circular shape, having one of the followingconfigurations:

-   -   the round cutting edge 522EA has a diameter equal to the        diameter of the elongated cavity, such that the cutting edge is        created by sharpening (grinding) in the direction from the outer        diameter of the inner member towards the diameter of the        elongated cavity;    -   the round cutting edge 522EA has a diameter equal to the outer        diameter of the inner member, such that the cutting edge is        created by sharpening in the direction from the diameter of the        elongated cavity towards the outer diameter of the inner member;        and    -   the round cutting edge 522EA has a diameter bigger than the        diameter of the elongated cavity and smaller than the outer        diameter of the inner member, such that the cutting edge is        created by sharpening in both directions, from the outer        diameter of the inner member towards the diameter of the        elongated cavity and from the diameter of the elongated cavity        towards the outer diameter of the inner member.

It was found by the inventors that the degree of sharpening, i.e. theinclination angle, plays an important role in providing effectivelydesired piercing of and/or attachment to the tissue.

FIG. 5B illustrates another non-limiting example of the inner member520B. In this example, the inner member is configured as a full-bodied,not hollow, elongated member with a second distal part 522B configuredas a drill bit being provided with a flute enabling creating the desiredchannel in soft tissue while rotating. The length, spiral, point angleand lip angle of the drill bit can all be adjusted for optimal softtissue removal. In this instance, the inner member 522B rotates withfull rounds clockwise or anticlockwise, depending on the spiraldirection, such that the removed tissue is conveyed backwardly far fromthe target tissue and towards a collecting cavity located between theinner member and the outer member of the device.

FIGS. 5C1-5C3 illustrate another non-limiting example of the innermember 520C. FIG. 5C1 is an isometric view of the inner member 520C.FIG. 5C2 is an isometric view of the coaxial outer and members, 510C and520C, with half of the wall of the outer member at the distal sideremoved for easy illustration. FIG. 5C3 illustrates a transverse crosssection of the outer and inner members made along the line C-C in FIG.5C2. In this example, the inner member is configured partially similarto the example of FIG. 5A in that, as shown, the inner member 520C has asecond distal part 522C configured to attach to tissue and cut tissue byits cutting edge 522EC, while rotating and progressing distally, and toguide the inner member through the tissue. The inner member 520C alsoincludes a second proximal elongated part 524C that includes anelongated chamber/cavity 526C (inside the second proximal elongated part524C, shown in FIG. 5C3) configured to receive therein the tissue beingremoved. As also shown, the second proximal elongated part 524C of theinner member 520C includes a tissue trapper 524TC at a distal segment524DC of the second proximal elongated part 524C, located substantiallyin parallel to the elongated cavity 526C. The tissuetrapper/tissue-trapping enhancer 524TC enhances and contributes to thetrapping of the removed tissue during its removal, such that itallows/ensures pulling the removed tissue out of the body. In addition,the tissue trapper 524TC can facilitate the flow of the removed tissueinto the cavity 526C by minimizing issues of clogging. In someembodiments, additionally or alternatively, the cavity in the innermember of the device can be designed to trap or contribute to trappingof the tissue there inside. In this example, the tissue trapper 524TCincludes a slit 524SC, located in the longitudinal direction, i.e. alongat least part of the cavity 526C. The slit 524SC is obtained bytangential cutting of the round wall of the inner member along thedistal segment 524DC, i.e. by cutting in the tangential direction to theinner member's wall/circumference. It should be noted that generally thetissue trapper 524TC can include more than one slit along the innermember circumference, each slit being formed by tangential cutting alongthe longitudinal axis. FIG. 5C2 illustrates the device either during thepositioning phase or after the device has been pulled out of the body,while in both cases the inner member (and the removed tissue in theafter operation case) is located safely inside the outer member. Asshown in FIGS. 5C2 and 5C3 the tangential cutting of the inner member'swall forms, in addition to the slit 524SC, a depression 524D along thedistal segment 524DC of the inner member. The depression 524D causes theformation of a second outer cavity 528C between the inner and outermembers, that may enhance the pulling of the removed tissue towards thecavity 526C and/or the inside of the outer member 510C. In other words,the depression 524D, resulting from the tangential cutting, forms partof the tissue trapper 524TC.

FIGS. 5D1-5D3 illustrate another non-limiting example of the innermember 520D including a tissue trapper/tissue-trapping enhancer 524TD.FIG. 5D1 is an isometric view of the inner member 520D. FIG. 5D2 is anisometric view of the coaxial outer and members, 510D and 520D, withhalf of the wall of the outer member in the distal side removed for easyillustration. FIG. 5D3 illustrates a transverse cross section of theouter and inner members made along the line D-D in FIG. 5D2. As can beappreciated, various features and elements in FIGS. 5D1-5D3 are similarto those in FIGS. 5C1-5C3. Specifically, as shown in FIG. 5D1, the innermember 520D has a second distal part 522D configured to attach to tissueand cut tissue by its cutting edge 522ED, while rotating and progressingdistally, and to guide the inner member through the tissue. The innermember 520D also includes a second proximal elongated part 524D thatincludes an elongated chamber/cavity 526D (inside the second proximalelongated part 524D, as shown in FIG. 5D3) configured to receive thereinthe tissue being removed. The second proximal elongated part 524D of theinner member 520D includes a tissue trapper 524TD at a distal segment524DD of the second proximal elongated part 524D, located substantiallyin parallel to the elongated cavity 526D. As has been explained, thetissue trapper 524TD enhances and contributes to the trapping of theremoved tissue during its removal, such that it allows/ensures pullingthe removed tissue out of the body. In addition, the tissue trapper524TD can facilitate the flow of the removed tissue into the cavity 526Dby minimizing issues of clogging. In some embodiments, additionally oralternatively, the cavity in the inner member of the device can bedesigned to trap or contribute to trapping of the tissue there inside.In this example, the tissue trapper 524TD includes a slit 524SD, locatedin the longitudinal direction, i.e. along at least part of the cavity526D. The slit 524SD is obtained by radial cutting of the round wall ofthe inner member along the distal segment 524DD, i.e. by cutting in theradial direction of the inner member. It should be noted that generallythe tissue trapper 524TD can include more than one slit along the innermember's circumference, each slit being formed by radial cutting in theradial direction and along the longitudinal axis. FIG. 5D2 illustratesthe device either during the positioning phase or after the device hasbeen pulled out of the body, while in both cases the inner member (andthe removed tissue in the after operation case) is located safely insidethe outer member.

Turning now to FIGS. 5E1 to 5E7 illustrating one non-limiting scenarioof removing soft tissue from a tissue layer in the body. Specifically,the figures illustrate undesired effect of tearing of the soft tissue,instead of or in addition to cutting, while rotating the cutting toolinside the tissue.

Ideally, the channel created in the tissue can be expected to look asshown in FIG. 5E1, i.e. it should have a cylindrical shape, such as whenthe inner member is as described in FIG. 5A. The channel 5003 connectsbetween outer scleral surface 5002 and inner scleral surface 5001. Thecutting tool 520E, e.g. the inner member, rotates in a direction 503Earound its longitudinal axis, either clockwise or anticlockwise orreciprocating in both directions, and approaches the sclera underfeeding rate 502E. In preferable scenario, the channel should have therequired dimensions while its diameter is similar to the diameter of thecutting edge 522EE. The removed tissue 5004 is expected to be trappedwithin the cutting tool 520E as shown in FIG. 5E2.

It is appreciated that cutting of the tissue is defined by the tissuebehavior and characteristics. As the cutting tool 520E cuts, itrotates/revolves within the tissue. The treated organ (e.g. —the eye) isstatic while the cutting tool 520E rotates/turns. The cutting tool 520Epresses the tissue both by its external surface 504E (outer diameter)and inner diameter 505E. The diameter of the cylindrical tissue 5004 isdefined by the cutting edge 522EE yet the inner diameter 505E might beslightly smaller and causes squeezing of the tissue (within the cavityof the cutting tool). Another reason for squeezing of the tissue insidethe cavity of the cutting tool can be a relatively high friction forcebetween the tissue and the inner surface of the cavity. Additionalreason for squeezing of the tissue inside the cavity might be thelimited length of the cavity as shown in FIG. 5E3 which is a magnifiedimage of a cutting tool, captured by a microscope. The currenttechnology enables creating a cavity with a small diameter, as requiredin the treatment of the eye, with length up to about 0.5 mm, asillustrated by the step 508E in the figure. However, the required lengthfor the channel may be longer than that, for example it should be aboutthree times more (1.5 mm) when the channel is to be created in thesclera in the eye wall.

Since the cutting tool 1 (e.g. the inner member) rotates and the tissue(e.g., the eye) is static, the tissue 5004 is expected to remain staticuntil the cutting process is completed. In reality, during the cuttingprocess, as shown in FIGS. 5E4 and 5E5, the tissue 5004 is defined bytwo sections, tissue section 5041 pressed into the cavity of the cuttingtool and tissue section 5042 still un-pressed. The attachment of tissuesection 5041 to the inner surface of the cavity, due to high friction ordue to insufficient cavity length, may cause tissue section 5041 tostart rotating with the cutting tool and to tear apart from tissuesection 5042. In this case, the separation of tissue 5004 is not causedby cutting, but rather by torsional tearing. Accordingly, the channelcreated within the eye wall might look as shown in FIG. 5E6 or 5E7. Thismay result in insufficient and ineffective drainage, or even no drainageat all.

Minimizing the radial attachment of the removed tissue to the innersurface of the cavity in the cutting tool enables continuation ofcutting rather than tearing. Reducing the radial attachment forcebetween the removed tissue (e.g., tissue 5041) and inner surface of thecavity (e.g., surface 505E) can be achieved by lowering the frictioncoefficient between the tissue and the inner surface of the cavity (forexample by applying low friction coating on the inner surface).Alternatively or additionally, Reducing the radial attachment betweenthe removed tissue and inner surface of the cavity can be achieved bycreating specific geometry of the cutting tool, e.g. by making thediameter of the inner surface of the cavity bigger than the diameter ofthe cutting edge of the cutting tool.

Turning now to FIGS. 5F-5G showing non-limiting exemplary embodiments oftissue cutting tools and methods of fabrication and/or optimization. Thecutting tools are optimized for cutting soft tissue and for creating achannel with predetermined dimensions and geometry in a specific giventissue while minimizing the effect of tearing. In some embodiments, theinner member of the device of the invention can be configured as thecutting tools described in FIGS. 5F and 5G. Therefore, the referencenumbers used in the following figures follow the same numbering used sofar, for example 520E denotes a tissue cutting tool that can be used asthe inner member of the device of the invention. However, this shouldnot be interpreted as limiting the invention.

FIG. 5F shows a first non-limiting example of a cutting tool configuredaccording to some embodiments of the present invention. The figuredescribes a cutting tool 520E which can minimize the radial attachmentbetween the removed tissue and the cavity's inner surface to therebyminimize the effect of tearing of the tissue. This can be achieved byshaping of the cutting tool. As shown in the figure, a distal portion504F of the cutting tool is shaped and pressed towards rotation axis ofthe tool (passing at the center of the tool if the tool is symmetricaland isotropic). Pressing and shaping can be made by means of knowntechniques, such as swaging and spinning. In this case, the diameter ofthe cutting edge 522EF at the distal end of the cutting tool is smallerthan the inner diameter 505F of the cavity inside the cutting tool. Asthe diameter of the cutting edge determines the diameter of the removedtissue, the cutting tool 520F is expected to provide minimal or noattachment force on the removed tissue inside the tool and by thisimprove the trapping of the removed tissue, while minimizing tearingrisk and preserving full shape of the removed tissue that matched a fullopen channel inside the tissue wall.

FIGS. 5G1 to 5G4 illustrate non-limiting exemplary cutting tools 520G1(in FIG. 5G3) and 520G2 (in FIG. 5G4) and an exemplary process forproducing the cutting tools (FIGS. 5G1 and 5G2), according to someembodiments of the invention.

In FIG. 5G1, a side view (cross section) of tool 520G includes at adistal side 501G a hollow cylinder 506G having a cavity 507G betweenuniform outer and inner diameters, 504G and 505G respectively, thatextend along a longitudinal (rotation) axis X1. In FIG. 5G2, a close-upview on the cylinder 206G is shown. A distal portion 504G is shaped witha predetermined pattern, e.g. by pressing, such that both the inner andouter diameters decrease towards the distal end 509G of the hollowcylinder. As shown on the proximal end 511G of the hollow cylinder, theoriginal inner and outer diameters are about 0.17 mm and 0.3 mmrespectively, and the modified inner and outer diameters at the distalend 509G are about 0.13 mm and 0.27 mm respectively. The shaping of thedistal portion can be done by, for example but not limited to, swagingand/or spinning techniques. The pattern of shaping can be linear, forexample by tapering the distal portion to provide a substantiallycylindrical frustum shape, or non-linear, e.g. by following a curvedline such as parabolic or other similar pattern.

In a next step, a slice of the hollow cylinder's side wall is removed(to the right, in the figure) along the longitudinal axis, in theproximal direction, starting from the distal end 509G. Depending on theslice depth (i.e. thickness), two exemplary cutting tools 520G1 and520G2 are shown in FIGS. 5G3 and 5G4. A cutting edge 522EG is formed atthe distal end and the inner and outer diameters become almost equal,such as 0.18 mm in FIG. 5G3 and 0.16 mm in FIG. 5G4. Additionalsharpening of the cutting edge, both from inside and outside directionsresults in that the cavity, at a distal side thereof, has a slightlysmaller diameter than the cutting edge's diameter. Then, the innerdiameter of the cavity increases continuously in the proximal direction(to the right in the figures) until the inner diameter of the cavityreaches the higher value 505G of the proximal side of the hollowcylinder. Alternatively, the slicing of the inner surface of the cavitymay provide a substantially constant inner cavity diameter. By thisslicing step, no step (such as step 508E in FIG. 5E3) is present, andthe cavity will have at least a length, in the longitudinal axisdirection, equal to the original hollow cylinder's cavity length, thusproviding receiving cavities longer than the limit of 0.5 mm and wideenough to thereby minimize attachment of the tissue entering the cavityto the inner surface of the cavity. All at a micro level required forapplications such as creating safe enough channels in the eye wall.

Other non-limiting examples of the inner member include devices asdescribed in WO2013186779 and WO2015145444 both assigned to the assigneeof the present invention.

As described above, the various movements of the outer and inner memberof the device are performed either manually and/or by using amoving/movement mechanism. The outer member is configured for axialmovement only, while the inner member is configured for both rotationaland axial movements. Typically, the inner member's rotation is governedby an electrical motor connected to the proximal side of the innermember. This is not particularly described here, examples can be foundin the above mentioned patent application PCT/IL2016/051063 assigned tothe assignee of the present invention. In the following, a variety ofmoving/movement mechanisms are described.

Reference is made to FIGS. 6A to 6D illustrating a non-limiting exampleof a movement mechanism configured for manual movement of the deviceduring operation. As shown, the device 600 includes outer member 610 andinner member 620 mounted on a handle 650 via a movement mechanism 640.FIGS. 6A and 6C show the device during the positioning phase, i.e. whenthe outer member is moved forwardly (by manual pushing of the handle bythe operating surgeon) to pierce first (preceding) and second (target)tissue layers, or to approach and stick into the target layer directly(such as in the Ab interno procedure). FIGS. 6B and 6D show the deviceduring the channeling phase, i.e. when the inner member is rotated, byan electric motor (not shown), and advanced distally to cut and removetissue, thereby leaving the channel in the target tissue layer.

The movement mechanism 640 includes a latch 642, a spring 644, and ahousing 646. As shown in FIG. 6C, the latch is movable to the sides asillustrated by the arrow A. The outer member 610 is axially locked bybeing firmly attached to the housing at B and supported by the latch 642at C. The spring 644 is slightly pre-compressed/relaxed during thepositioning phase.

After pushing the device with the handle 650 inside the tissue until thefirst distal part of the outer member is stuck/anchored temporarilyinside the target tissue layer, e.g. in the sclera, as described above,the operating surgeon turns the latch 642 to the left (or to the right)releasing the outer member 610 at C, thus enabling its retractionproximally. The surgeon switches the electrical motor to rotate theinner member and pushes distally with the handle 650 to expose the innermember 620 as in FIG. 6D. The outer member 610 retracts and the spring644 is compressed. The channel creation occurs once the surgeon pushesthe device distally. While the compressed spring 644 tends to push theouter member 610 distally, the spring's constant is chosen to be too lowto enable further penetration of the outer member to the sclera.Ergonomically, the surgeon can control over all features using a singlefinger while holding the handle.

Reference is made to FIGS. 7A to 7D illustrating another non-limitingexample of a movement mechanism configured for manual movement of thedevice, specifically the inner member, during operation. As shown, thedevice 700 includes outer member 710 and inner member 720 mounted on ahandle 750 via a movement mechanism 740. FIGS. 7A and 7C show the deviceduring the positioning phase, i.e. when the outer member is movedforwardly (by manual pushing of the handle by the operating surgeon) topierce one or more tissue layers and/or until being inserted andanchored in the target tissue layer. FIGS. 7B and 7D show the deviceduring the channeling phase, i.e. when the inner member is rotated, byan electric motor, and advanced distally to create the channel in thesecond tissue layer.

The movement mechanism 740 is configured for controllably advancing theinner member (distally) by manual pushing movement. As shown in FIG. 7C,the movement mechanism 740 includes a knob 742, a spring 744, and ahousing 746. The outer member 710 is axially locked by being fixedlyattached to the housing at D, and as a result also to the handle 750,such that when the operating surgeon pushes the handle 750 towards thetissue, the outer member moves in the axial direction and penetrates thetissue until it sticks in the sclera. The spring 744 is relaxed duringthe positioning phase.

The knob 742 is attached to the proximal side of the inner member 720 atE, such that they move together in the distal and proximal directions.During the channeling phase, the knob 742 is controllably pushed in thedistal direction by the operating surgeon, as shown by arrow R, againstthe spring 744 causing it to compress. The inner member moves distallyat the same rate by which the operating surgeon pushes the knob 742.Upon releasing the knob 742, a retraction movement occurs, the spring744 relaxes and pulls the knob 742 as well as the inner member 720proximally to the closed state as in FIG. 7C. Additionally, though notspecifically illustrated, the movement mechanism may include a latchconfigured to lock the knob 742 in the forward position, and only whenthe latch is released by the operating surgeon, the retraction movementoccurs. As mentioned, the rotational movement of the inner member iscontrolled by an electrical motor which is not specifically describedherein.

Reference is made to FIGS. 8A to 8D illustrating another non-limitingexample of a movement mechanism configured for manual movement of thedevice, specifically the inner member, during operation. As shown, thedevice 800 includes outer member 810 and inner member 820 mounted on ahandle 850 via a movement mechanism 840. FIGS. 8A and 8C show the deviceduring the positioning phase, i.e. when the outer member is movedforwardly (by manual pushing of the handle by the operating surgeon) topierce one or more tissue layers and/or until being inserted andanchored in the target tissue layer. FIGS. 8B and 8D show the deviceduring the channeling phase, i.e. when the inner member is rotated, byan electric motor (not shown), and advanced distally to create thechannel in the target tissue layer.

The movement mechanism 840 is configured for controllably advancing theinner member (distally) by manual pulling movement. As shown in FIG. 8C,the movement mechanism 840 includes a knob 842, a spring 844, and ahousing 846. The outer member 810 is axially locked by being fixedlyattached to the housing at F, and as a result also to the handle 850,such that when the operating surgeon pushes the handle 850 towards thetissue, the outer member moves in the axial direction and penetrates thetissue until it sticks in the sclera. The spring 844 is relaxed duringthe positioning phase.

The knob 842 is attached to the proximal side of the inner member 820 atG, such that they move together in the distal and proximal directions.During the channeling phase, the knob 842 is controllably pulled in theproximal direction by the operating surgeon, as shown by arrow W, suchthat G moves distally against the spring 844 causing it to compress. Theinner member moves distally at the same rate by which the operatingsurgeon pulls the knob 842. Upon releasing the knob 842, it moves in thedistal direction, the spring 844 relaxes and pushes G as well as theinner member 820 proximally to the closed state as in FIG. 8C.Additionally, though not specifically illustrated, the movementmechanism may include a latch configured to lock the knob 842 in thebackward position, and only when the latch is released by the operatingsurgeon, the retraction movement of the inner member occurs. Asmentioned, the rotational movement of the inner member is controlled byan electrical motor which is not specifically described herein.

Reference is made to FIGS. 9A to 9E illustrating another non-limitingexample of a movement mechanism configured for advancement of the innermember under constant or substantially constant force, e.g. 5-6N (withtolerance of about 1N). FIGS. 9A and 9B show the whole device 900. Asshown, the device 900 includes outer member 910 and inner member 920mounted on a handle 950 via a movement mechanism 940. FIGS. 9A, 9C and9D show the device during the positioning phase, i.e. when the outermember is moved forwardly to pierce one or more tissue layers and/oruntil being inserted and anchored in the target tissue layer (all bymanual pushing of the handle by the operating surgeon). FIGS. 9B and 9Eshow the device during the channeling phase, i.e. when the inner member920 is rotated, by an electric motor, and advanced distally to createthe channel in the target tissue layer.

The movement mechanism 940 includes a knob 942, a spring 944, a floatingdisk 948 and a housing 946 including three pins 946P firmly receivedtherein in a spaced-apart relationship matching the floating disk'steeth. The outer member is permanently attached to the housing 946 suchthat it does not move relative to the handle 950, and the outer member'saxial movement is generated only by the operating surgeon by pushing thehandle forwards and pulling it backwards.

During the positioning phase, as shown in FIG. 9C, the spring 944 iscompressed applying a distal pushing force on the floating disk 948.However, the floating disk is kept stationary while the knob 942 isengaged with the floating disk 948 preventing from moving.

As shown in FIG. 9D, after the outer member is inserted and anchored inthe sclera, the operating surgeon turns on the electrical motor to causerotation of the inner member, then turns the knob to the right or leftand releases the floating disk 948. Once the floating disk is releasedit turns and is pushed distally by the spring 944 which starts to relax,the floating disk engages with the pins 946P, as shown in FIG. 9E. Thefloating disk 948 is also axially attached to a base of the innermember, such that the floating disk's distal movement under the constantrelaxing force of the spring 944 causes the rotating inner member tomove distally under a constant force until the floating disk reaches thedistal side of the housing 946 and the axial movement stops.Additionally, though not specifically illustrated, the movementmechanism may include a latch configured to lock the knob 942, and onlywhen the latch is released by the operating surgeon, the retractionmovement of the inner member occurs.

Reference is made to FIGS. 10A to 10D illustrating another non-limitingexample of a movement mechanism configured for advancement of the innermember under constant rate. FIGS. 10A and 10B show the whole device1000. As shown, the device 1000 includes outer member 1010 and innermember 1020 mounted on a handle 1050 via a movement mechanism 1040.FIGS. 10A and 10C show the device during the positioning phase, i.e.when the outer member is moved forwardly to pierce one or more tissuelayers and/or until being inserted and anchored in the target tissuelayer (by manual pushing of the handle by the operating surgeon). FIGS.10B and 10D show the device during the channeling phase, i.e. when theinner member 1020 is rotated, by an electric motor, and advanceddistally to create the channel in the target tissue layer.

The movement mechanism 1040 is configured for automatic rotation andadvancement of the inner member. The rotation and advancement movementscan be executed by the same or different motors. Additionally, the rateof the rotation and advancement movements can be the same or different,regardless of whether one or two separate motors are employed.

As shown in FIGS. 10C and 10D, the movement mechanism 1040 includes twogears G1 and G2. Gear G1 receives, at a first rate (e.g. 100-500 roundsper minute (RPM)), the rotational power delivered by the motor (which isnot shown). Gear G1 rotates with the inlet shaft 1062 which isconstantly connected to Gear G1 and is responsible for the rotationalmovement of the inner member 1020. The inner member is connected to theinlet shaft 1062 via an outlet shaft 1064 which rotates together withthe inlet shaft 1062 yet it can move axially with respect to the inletshaft 1062. Gear G2 is engaged with gear G1 such that it rotatesaccording to a predetermined ratio between G1 and G2. Gear G2 isresponsible for the axial movement of the inner member as shown in FIG.10D. Gear G2 is connected constantly to a parallel shaft 1066 that has abuilt-in driving thread, as shown, such that the rotational movement ofthe Gear G2 and the parallel shaft 1066 is translated to an axialmovement, of a driving nut 1072, via the built-in driving thread. Theaxial movement of the inner member is controlled by the housing's 1046length along the axial direction. The driving nut 1072 is driven by therotation of the parallel shaft 1066, via the built-in thread, such thatit moves to the distal direction and forces the outlet shaft 1064distally with it. A bearing 1074 between the driving nut 1072 and outletshaft 1064 enables the outlet shaft to rotate as it moves axially whilea fork-like shaft 1076 enables the outlet shaft to continue turningalong the axial distal travel.

The invention claimed is:
 1. A medical device configured and operablefor removing a defined shape of soft tissue from a target tissue layerin an eye thereby creating a matching channel with predeterminedgeometry and orientation between two side walls of the target tissuelayer to enable drainage of fluid from the eye through the channel, thedevice comprising coaxial outer and inner elongated members extendingalong axis X; said outer member comprising an open distal side and afirst distal part configured for sticking to said target tissue layerduring forward axial movement; said inner member comprising: a seconddistal part configured to rotate and project distally, along said axisX, through said open distal side of the outer member, the second distalpart being open at a distal end thereof and comprising a round cuttingedge having a first diameter, the cutting edge being configured toattach to said target tissue layer and cut said shape of the soft tissuefrom the target tissue layer while rotating and progressing, therebycreating said channel formed as a hole through the target tissue layer,and retract backwardly into said outer member, and a chamber extendingproximally from said open second distal part to a proximal end of thechamber, the chamber being configured to retain and store said removedshape of soft tissue in said removed shape of soft tissue's intact form,thereby providing a validation and authentication to the volume andshape of the corresponding channel created inside the target tissuelayer wherein said chamber has one of the following configurations: a)the chamber has dimensions matching said predetermined shape of the softtissue, said predetermined shape of the soft tissue is cylindrical andhas a length of about 1.5 mm and a diameter of between about 0.1 mm andabout 0.2 mm; b) the chamber has a length of at least the length of theremoved tissue and has a chamber diameter smaller than said firstdiameter at a distal end of the chamber and which increases continuouslytowards the proximal end of the chamber; or c) the chamber has a lengthof at least the length of the removed tissue and has a constant chamberdiameter being equal to said first diameter, and wherein said firstdiameter is between about 0.1 mm to about 0.2 mm.
 2. The medical deviceaccording to claim 1, wherein said first distal part is configured forpenetrating at least one other tissue layer preceding said target tissuelayer during said forward axial movement, said first distal partcomprises a tissue piercing tip at a distal end of the first distal partconfigured and operable to penetrate said at least one other tissuelayer and said target tissue layer and a proximal portion at a proximalside of the first distal part configured and operable to penetrate saidat least one other tissue layer and to stop at said target tissue layer,thereby sticking said outer member in the target tissue layer.
 3. Themedical device according to claim 2, wherein said first distal part hasa predefined length such that said tissue piercing tip does not exitdistally from said target tissue layer.
 4. The medical device accordingto claim 2, wherein said proximal portion is a rim of said outer member,formed by cutting a section of wall of the outer member along said axisX.
 5. The medical device according to claim 1, having at least one ofthe following configurations: a) said inner member is fixedly attachedto and housed within said outer member during said forward axialmovement of said outer member; or b) said outer member is manually movedduring said forward axial movement until said sticking of said outermember in said target tissue layer.
 6. The medical device according toclaim 1, having one of the following configurations: a) said innermember, while rotating, is manually moved along said axis X to createthe channel; b) the device comprising a constant-force moving mechanismconfigured and operable to move said inner member, while rotating, alongsaid axis X under a constant force; c) the device comprising a constantrate moving mechanism configured and operable to move said inner member,while rotating, along said axis X with a constant rate; or d) the devicecomprising an electric motor configured and operable for axially movingand or rotating said inner member.
 7. The medical device according toclaim 1, wherein said inner member comprises an elongated round bodyextending along the longitudinal axis X and has a uniform outer diameterat a proximal side thereof, said first diameter of the round cuttingedge being smaller than said outer diameter and said second distal parthas a continuously decreasing outer diameter towards the distal end. 8.The medical device according to claim 1, wherein said inner membercomprises a tissue trapper comprising a slit formed in wall of the bodyof inner member along at least part of said chamber, said slit is formedby one of the following: a) tangential cutting of the wall of the bodyof inner member, said device thereby further comprising an outer chamberlocated between the inner and outer members, b) radial cutting of thewall of the body of inner member.
 9. The medical device according toclaim 1, wherein said rotating of said second distal part comprisesclockwise and anti-clockwise reciprocal movement.
 10. The medical deviceaccording to claim 1, wherein said first distal part of the outer memberis formed by cutting the outer member in the direction of the axis Xalong a curved line chosen to provide smooth penetration, at a distalsegment of the first distal part, with increasingresistance-to-progression force, at a proximal segment of the firstdistal part.
 11. The medical device according to claim 1, wherein saidpredetermined geometry and orientation of the channel are selected toenable pressure regulation of a treated eye over a predetermined timeperiod.